Valve-timing system



Jan. 18, 1927.

J. N. BARTLETT I VALVE TIMING SYSTEM Filed April 17, 1925 3 Sheets-Sheet 2 1,614,861 J. N. BARTLETT VALVE TIMI-NG SYSTEM Filed April 17, 1925 3 Sheets-Sheet :3

Jan. 18,1927.

m/wiz- ATTNNEY Patented Jan. 18, 1927.

UNITED STATES JOHN N. BARTLETT, OF WINNIPEG, MANITOBA, CANADA.

VALVE-TIMING- SYSTEM.

Application filed April 17, 1925.

This invention contemplates the provision of a changeable valve timing mechanism for internal combustion engines, wherein the timing of valves can be regulated for a normal or low speed, or changed for high speed, the change being made while the engine is in operation.

In carrying out the invention, I contemplate the use of a high and low cam for each valve, the cams being arranged in pairs on the cam shaft, and used in connection with means whereby the valve tappets can be operated by either set of cams as the occasion may require.

The nature and advantages of the invention will be better understood when the following detailed description is read in 0011- nection with the accompanying drawings, the invention residing in the construction,

combination and arrangement of parts as claimed.

In the drawings forming part of this application, like numerals of reference indicate similar parts in the several Views, and wherein:

Figure 1 is a horizontal sectional view through the crank case of an engine showing the cam shaft and the valve timing mechanism in plan.

Figure 2 is a view taken on line 22 of Figure 1.

Figure 3 is a view taken on line 33 of Figure 1.

Figure L is a View showing the valve tappets arranged for use with one set of cams.

Figure 5 is a sectional view through one of the rocker arms.

Figure 6 is a fragmentary sectional view of the hand and foot controlled elements through the 'instrumentality of which the valve timing mechanism is operated.

Figure 7 is a View similar to Figure 1 of a modified form of the invention.

Figure 8 is a sectional view on line 88 of Figure 7. y

Referring to the drawings in detail, and particularly to Figures 1 to 6 inclusive, 10 represents generally an internal combustion engine, wherein the cam shaft is indicated at 11, and the valves at 12. Each valve is provided with a valve stem 13 which is adapted to be actuated by a valve tappet 1 1 in the usual well known manner. For each valve tappet 14, the cam shaft'is provided with what I term a high speed cam 15 and a low speed cam 16, so that the timing of the Serial No. 23,873.

valves can be changed for a normal or low speed, or for a high speed of the motor while the latter is in operation.

In accordance with one embodiment of the invention, I employ a shaft 17 upon which is mounted the usual rocker arm 18, these arms being arranged to overlie the cam shaft 11 and support the valve tappet 14 as clearly shown in Figure 3. Projecting from the shaft 17 adjacent the ends thereof are spaced parallel arms 19 which arms support a rod 20 which is located directly beneath the rocker arms in the position shown in Fi ure 3. It might here be stated that the sha t 17 is not only mounted in its bearings for partial rotation, but is also susceptible of longi tudinal sliding movement, so that the rocker arms 18 can be conveniently and easily shifted to overlie the high speed cams 15 or the low speed cams 16 on the cam shaft 11 as'the occasion may require.

For this purpose, I provide the shaft 17 with a right angularly disposed extension 21, the outer end of which has a ball and socket connection with an obliquely disposed rod 22, the other end of which rod is connected with a rod 23 which in turn is connected as at 24 with the shank 25 of a foot pedal 26. This foot pedal 26 is arranged adjacent the floor board 27 of a vehicle being mounted for horizontal slidin movement, and is utilized to rotate the shaft 17 against the tension of a spring 28 to elevate the rocker arms 18 when it is desired to shift the latter from one set of cams onto the other. The rod 22 is provided with a collar 29 adaptedto ride along the upper surface of a slotted bracket 30 through which the rod 22 operates, so that it is obvious that when the foot pedal 26 is moved inwardly, the rod 22 is moved through the bracket in one direction. During this movement of the rod, the collar 29 forces the rod in the direction of the shaft- 17, and if this rod 22 is connected with the arm 21 of the said shaft, the latter is rotated in a direction to elevate the rocker arms 18. It is manifest that movement of the rod 21 will rotate the shaft 17 which will elevate arms 19 and rod 20, thereby raising rocker arms 18, so that the shaft 17 can be moved longitudinally. As above stated, the shaft is rotated in this direction against the tension of the spring 28, so that when the pedal is released, the spring functions toreturn the rocker arms to the active positions, by re versing the rotation of the shaft 17.

the instrumentality .of the rod 20'.

The shaft projectsbeyond one end of the engine casing and is provided with a' grooved collar 17 to accommodate the yoke extremity of a bell crank lever as clearly shown in Figure 6. This lever is pivoted on a bracket 18, one branch being associated with the shaft 17 in the manner just mentioned while the other branch 19' is connected by a rod 20 with the adjacent branch 31 of a bell crank lever pivoted as at 32 upon a suitable bracket 33. The other branch 34 of the bell crank lever is connected with a manually operable rod 35 which is mounted for sliding movement in a horizontal plane and formed with a knob or handle 36. This rod 35 is employed to move the shaft 17 longitudinally in either direction after the rocker arms 18 have been elevated above the cams. In other words, the rocker arms normally operate with the low speed cams above referred to, so that the valves 12 are properly timed for a normal or low speed. When, the speed of the motor is increased and it is desired to change the timing of the valves accordingly, it is only necessary to press upon the'foot pedal 26 to rotate the shaft '17 in a direction to elevate the rocker arms 18. The grooved collar 17 allows the shaft to rotate in the forked extremity of the bell crank lever associated therewith. Just soon as this is done, the rod 35 is operated to shift the shaft 17 longitudinally of.the cam shaft, thus arranging the rocker arms above the high speed cams. Manifestly when therod 35 is operated, the bell crank lever 31 is rocked upon its pivot, and imparts rocking movement to the bell crank lever associated with the shaft ,17, through Arranged within the motor casing is a bracket 37 which may be of any suitable construction anddesigned to engage the adjacent arm 19 carried by the shaft 17, to holdthe shaft'in its adjusted position. Just as soon as the foot is removed from the pedal 26, the spring 28 functions to lower the rocker arms to their active positions.

It is also desired to short circuit the igni tion system when the timing of, the valves is being changed, and for which ,purpose,.I make use of tubular casing 39 of insulated material which is slotted as at 40 to receive a finger 4E1 projecting fromthe ,foot operated shank 25'arranged within this casing 39 and disposed in the path of movement of the finger 41 is a coiledspring 4-2 to which one end of a ground wire 43 is connected. Manifestly, when the pedal 26 is moved inwardly, the arm 41 is brought'into contacting engagement with the spring 42 thereby grounding or short circuiting the ignition circuit momentarily or until the pedal 26 is released.

In Figures 7 and 8, I have illustrated a modified form of'the invention, which is This shaft is provided with a stop collar 16 adapted to limit the movement of the shaft in one direction by contacting the ad acent bearing, while the opposite end of the shaft is adapted to contact the plate 47 associated with the other bearing to limit the move ment of the shaft in an opposite direction. This shaft 4 1- isprovfded with a low and high speed cam as and 49 respectively for each valve tappet 50, so thatby adjusting the shaft -14 either set of cams can be arranged for use with the respective valve tappets, thus changing the timing of the valves for a proper speed of the motor as the occasion may require. lvhile any suitable means maybe employed for shifting or adjusting the cam shaft for this purpose, I employ a foot operated rod 51 which has secured thereto a yoke 52 which adapted to straddle a collar 53 with which it. is connected, the'collar be ng fixed upon the cam shaft 14:. The rod 51 is mounted for sliding movement to a suitable bearing 54 and is formed with spaced notches 55 adapted to singly receive a spring pressed pin through the instrumentality of wh ch the said rod 51 and shaft 4 1- are held fixed in theirigiven positions. The rod 51 is adapted to return to normal position and released by a suitablespring not shown. The cams in this form of the invention are much wider than normally necessary, in order to allow the cams to be placed on the cam shaft in such a position that when the camshaft moved longitudinally, the cams will come into contact with the tappets, following one after the other. This placing or arrange ment of the cams makes it necessary to move the shaft further than the normal width of cams. This arrangement is necessary to provide for free, unobstructed longitudinal movement of the cam shaft, atsuch times when two or more cams are about to engage their respective tappets.

lVhile it is believedthat from the foregoing description, the nature and advantages of the invention will be readily apparent, Idesire to have it undesrtood that I do not limit myself to what is hereinshown and described, and that such changes may be resorted to when desired asifall within the scope of what is claimed.

Having thus described the invention, I claim:

1. A changeable valve timing mechanism for internal combustion engine, including a cam shaft, high and low speed cams carried by the shaft for each valve, rocker arms arranged to cooperate with saidcams, foot operated means for lifting said armsabove the cams, and operating means for subs quently shiftingthe arms for use witheither set of cams, and means for lowering said arms into active positions when said foot operated means is released.

2. A changeable valve timing mechanism for an internal combustion engine, including a cam shaft, a set of high speed cams, and a set of low speed cams carried by the shaft for said valves, rocker arms adapted to cooperate with either set of cams, means including a rod arranged beneath all of said arms and operable to lift the latter away from said cams, means for subsequently shifting said arms longitudinally of the cam shaft to arrange said arms for use with either set of cams, and means for lowering said arms into active positions when the first mentioned means is released.

3. A changeable valve timing mechanism for an internal combustion engine, including a cam shaft, a set of high speed cams, and a set of low speed cams carried by said shaft for said valves, a second shaft mounted for both rocking and sliding movements, rocker arms carried by the second mentioned shaft and adapted to cooperate With either set of cams, means for rocking said shaft to raise the arms above the cams, means for subsequently shifting the shaft longitudinally to position the arms for use with either set of cams, and means for subsequently lowering the arms to active positions when the first mentioned means is released.

4. A changeable valve timing mechanism for an internal combustion engine, including a cam shaft, a set of high speed cams, and a set of low speed cams carried by said shaft, a second shaft arranged parallel with the cam shaft and mounted for both rocking and sliding movements, rocker arms carried by the second mentioned shaft and adapted to cooperate with either set of cams, means including a rod supported by the second mentioned shaft for lifting all of said arms when the shaft is rocked in one direction, means for subsequently shifting said shaft to position said arms for use with either set of cams, means for holding said shaft in its adjusted position, and means for rocking the shaft in a reverse direction to lower said arms into their active positions when the first mentioned means is released.

5. A changeable valve timing mechanism for an internal combustion engine including a cam shaft, a set of high speed cams, and a set of low speed cams carried by'said shaft, a second shaft mounted for both rocking and sliding movements and arranged parallel with the cam shaft, rocker arms carried by the second mentioned shaft and adapted to cooperate with either set of cams, resilient means for normally holding said shaft and arms in an active position, foot operated means for rocking said shaft against the tension of said means to elevate said arms, means for subsequently shifting said shaft longitudinally to position said arms for use with the desired set of cams, and means for holding said shaft in its shifted position.

6. A changeable valve timing mechanism for an internal combustion engine comprising in combination with the ignition circuit thereof, a cam shaft, a set of high speed cams and a set of low speed cams carried by the shaft for said valves, rocker arms adapted to cooperate with either set of cams, means for lifting said arms away from the cams, means for subsequently shifting said arms to positions for use with either set of cams, while the motor is in operation, means under the control of the first mentioned means for short circuiting the ignition circuit while the change is being made, and means for returning said arms to their active positions when said first mentioned means is released.

In testimony whereof I affix my signature.

JOHN N. BARTLETT. 

